A communication network typically operates in accordance with a given standard or specification which sets out what the various elements of the network are permitted to do and how that should be achieved, i.e. the technology on which the communication is based on in the network. The standard may define whether a user of the network or more precisely, a user equipment is provided with a circuit switched service and/or a packet switched service. The standard may also define the communication protocols which shall be used for the connection. One or more of parameters requires for a communication session in the network are also typically defined.
In other words, the standard defines the “rules” and parameters on which the communication within the communication system is based on. Examples of the different standards and/or specifications include, without limiting to these, specifications such as GSM (Global System for Mobile communications) or various GSM based systems (such as GPRS: General Packet Radio Service), EDGE (Enhanced Data rate for GSM Evolution), AMPS (American Mobile Phone System), DAMPS (Digital AMPS), or 3rd generation (3G) communication systems such as the Universal Mobile Telecommunication System (UMTS), IMT 2000 (International Mobile Telecommunication System 2000), i-phone and so on.
User equipment that is to be used for communication via a communication network has to be designed to be compatible with the “rules” of the network. A user equipment may also be arranged to be compatible with more than one technology, i.e. a user equipment may communicate in accordance with different types of communication services. Such user equipment are often called as multi-mode terminals. The basic example of the multi-mode terminals is a dual-mode mobile station arranged to be compatible with two different communication networks.
A communication network is a cellular radio network consisting of accessing entities referred to as cells, hence the name “cellular system”. In most cases the cell can be defined as a certain area covered by at least one base transceiver station (BTS) that serves user equipment (UE) within the cell.
The user equipment (UE) within one of the access entities may be controlled by one or several control entities. Examples of the control entities include radio network controllers such as a base station controller (BSC) of the GSM system and a radio network controller (RNC) of the 3rd generation systems. An access network controller is in communication with appropriate core network (CN) control entities. The core network entities may comprise control nodes such as a mobile switching center (MSC), a serving GPRS support node (SGSN) and various gateway nodes such as a gateway GPRS support node (GGSN) or gateway mobile switching center (GMSC). The above list of the control entities is by no means exhaustive and other entities may also be implemented in the network. The network entities may also include nodes for storing information that associates with user equipment subscribing the network or visiting the network, such as appropriate home location registers (HLR) and visitor location registers (VLR). Depending the implementation, a register node may be integrated with another network entity.
A cellular system provides mobility for the user equipment in communication over a wireless interface with the network system. The user equipment is enabled to change from an access entity to another access entity. The change in the access entity may occur e.g. when a user equipment moves i.e. roams from a cell to another cell. The user equipment may change even from a network system to another network system, as long as the user equipment is compatible with the standard of said other system.
In order to be able to provide the mobility for user equipment with an ongoing (active) connection, the communication system may be adapted to hand the connection over from a serving control entity to another control entity. The handover of the connection may also be required for other reasons. For example, the quality of a packet switched connection may drop below a predefined threshold level, the access entity may become too congested, the user wishes to change the type or provider of a communication service and so on.
The handover should also be possible between two entities that belong to different network systems. If the new cell is not served by a similar system as the previous cell, then handover needs to be accomplished between communication systems that are based on different communication technologies and “rules”.
When a handover is to be accomplished between nodes of different communications systems (i.e. systems that are based on different communication technologies), it is possible that the “new” connection cannot be properly set-up due to differences in the operation of the various elements of the “new” (i.e. target) and the “old” communication systems.
FIG. 1 illustrates an example of the limitations of the prior art systems. More particularly, the example relates to a communication system wherein a user equipment may have a GSM and a UMTS session. The term “session” refers to any type of communication the user equipment may have, such as to a speech call, data call (e.g. web browsing) an so on.
A user can put an existing call or other communication session on hold and establish another session. A hold type service allows a server user equipment to interrupt communication on an existing active session and then subsequently, if desired, to re-establish the session. The traffic channel remains assigned to the user equipment after the communication is interrupted to allow the origination or possible termination of other communication sessions.
A service feature called “Support for Dual Services” is also known. This service feature enables two users on a point-to-point connection to use the connection for different types of information transfers during a single session but not at the same time. That is, a session may continue despite a change in the type of the communication. Examples of this type of services include supplementary services in which speech communication may be followed by data communication and speech and unrestricted data may alternate with each other.
Services such as intermediate calls and dual services may in some instances require a change in the channel configuration. However, the changing of the channel configuration may not be supported in a similar manner in two different networks, or one of the networks may not support any configuration changing mechanism.
If a negotiation during call establishment leads to recognition of this kind of services, an in-call modification procedure is allowed to be executed within the current call session by changing from one call mode to another. The in-call modification procedure, however, may require changes in the channel configuration while keeping the previously allocated channel. The required change may comprise allocation of a new channel, change in channel configuration parameters and so on.
The inventors have found that a handover between the different communication services may restrict the availability of this type of service features. For example, the above referenced services cannot be supported in a communication system comprising GSM and UMTS networks because the different network entities cannot always provide each other with information necessary to enable such a change. Furthermore, if a service feature such as the dual services is used or an intermediate call is established before a handover, this may prevent a successful intersystem handover to take place after the provided service has been modified.
In the FIG. 1 UMTS/GSM example the problem arises after a UMTS to GSM handover in a control entity that acts as a relay control entity (MSC-B). Such a handover is anticipated to occur substantially frequently. This is due, for example, the restricted coverage provided by the UMTS service. An operator may also wish to control the type of radio technology that is used to provide a particular service (e.g. speech or fax service). The operators may also wish to control any service provided for a particular class of users, e.g. the services provided for visiting subscribers from other national networks or second generation (2G) subscribers.
More particularly, the following procedures may take place in a FIG. 1 type arrangement.
At a session setup phase in the UMTS the user equipment sends a bearer capability (BC. 1) information element (IE) to the network. Based on the information within the bearer capability element, a serving MSC (MSC-A) derives UMTS quality of service (QoS) parameters that are needed for the radio bearer establishment. The bearer capability information element parameters can be mapped to Quality of Service (QoS) Radio Access Bearer (RAB) parameters during the session setup. The skilled person is familiar with the mapping operation. More information about the mapping can be found e.g. from 3GPP (third generation partnership project) technical specifications Nos. TS 23.107 and TS 23.910.
A UMTS to UMTS inter MSC (i.e. intrasystem) handover may be accomplished such that the serving i.e. anchor control entity (MSC-A) sends UMTS QoS parameters to the target i.e. relay control entity (MSC-B). After a UMTS to UMTS inter MSC intrasystem handover, Radio Access Network Application Part (RANAP) can be used as the access network protocol for signalling over an interface between the two control entities (MSC-A and MSC-B).
If a core network (CN) function of the UMTS needs to perform a handover towards the GSM service (UMTS to GSM handover), the relay control entity (MSC-B) performs an intersystem handover to the GSM by using GSM traffic channel parameters provided to it by the anchor entity (MSC-A).
The user may wish put the ongoing call on hold and establish a data call. In the call setup the user equipment sends the Bearer Capability (BC) describing the service to the anchor control entity (MSC-A) transparently via the relay control entity (MSC-B). Anchor MSC may then proceed an analysis whether the user is authorised to get that particular service and so on. The anchor MSC initiates assignment procedure towards the relay control entity (MSC-B) and the serving GSM BSS.
However, the relay control entity can only be aware of those channel parameters that associate with the active call. The parameter for the second call may be different from the parameters of the active call.
The inventors have found that this may be problematic. If the user puts at this point the ongoing session on hold and establishes a new session which requires a change of channel configuration by allocating a new channel, the session establishment will fail in the prior art arrangement since the description of the new channel is not known by the relay control entity (MSC-B). More particularly, the call establishment will fail in the FIG. 1 arrangement since the GSM Channel Type information element that associates with the intermediate data call and that is required for traffic channel assignment can not be sent to the target controller over an E-interface between the controllers. The call establishment fails also for the same reason in the case of dual services or other services wherein in-call modification is required. For example, this may occur when a speech service is followed by a data service.